1. Field of the Invention
The present invention relates to a liquid jet head which ejects liquid from nozzles to form images and letters on a recording medium or to form a functional thin film, and a liquid jet apparatus using the same.
2. Description of the Related Art
In recent years, there has been used an ink jet type liquid jet head which ejects ink droplets onto recording paper and the like to draw letters and diagrams, or ejects a liquid material onto a surface of an element substrate to form a functional thin film. The liquid jet head of this type is supplied with ink or a liquid material (hereinafter, collectively referred to as liquid) from a liquid tank via a supply tube, and ejects the liquid filled in channels thereof from nozzles communicated to the channels. At the time of liquid ejection, the liquid jet head and a recording medium for recording the jetted liquid are moved, to thereby record the letters and diagrams or form the functional thin film in a predetermined shape.
FIG. 6 is a transverse sectional view of an ink jet head in which two head chips 101 are stacked (FIG. 12 of Japanese Patent Application Laid-open No. 2004-209796). By stacking the two head chips 101, the number of nozzles is doubled to enable high density recording. Each of the head chips 101 includes a channel portion 115 sandwiched between a lower substrate 111 and an upper substrate 113, a nozzle plate 102 adhered to a front surface of the channel portion 115, a wiring board 103 adhered to an outer surface of the lower substrate 111, and a driver IC 132 mounted on the wiring board 103. The channel portion 115 is surrounded by the lower substrate 111, the upper substrate 113, and two walls (not shown) formed of a piezoelectric body which are sandwiched between the lower substrate 111 and the upper substrate 113.
The two head chips 101 are stacked under a state in which the upper substrates 113 thereof face each other and the lower substrates 111 thereof are on outer sides. The wiring board 103 is adhered to the outer surface of each of the two lower substrates 111. In other words, the two head chips 101 are sandwiched by the two wiring boards 103. The driver IC 132 is mounted on an inner surface of each of the wiring boards 103. Therefore, regions of the two head chips 101 opposite to a liquid ejection side are surrounded by the two wiring boards 103.
A control signal is input to the driver IC 132 mounted on the wiring board 103 from an external circuit such as a control circuit via a connector 133 and a wiring 134, and the driver IC 132 generates a drive signal for selectively driving each of the channel portions 115. The drive signal generated by the driver IC 132 is supplied via a driver wiring 131 to the channel portion 115. The two walls formed of the piezoelectric body deform in accordance with the drive signal to change the capacity of the channel portion 115. This causes liquid filled in the channel portion 115 to be ejected from nozzles.
Japanese Patent Application Laid-open No. Hei 10-146974 describes an ink jet head in which many actuator units having the same structure are stacked. One actuator unit includes a base plate having a plurality of groove-like ink chambers formed therein and a cover plate which is adhered to an upper surface of the base plate and which covers the plurality of ink chambers. The cover plate of an adjacent actuator unit is adhered to a bottom surface of the base plate. A nozzle plate is adhered to a front surface of the plurality of stacked actuator units in an ink ejection direction. Nozzles are formed in the nozzle plate at locations corresponding to the grooves in the base plate. The cover plate located between base plates has a projected portion protruding in a rear surface direction on a side opposite to the nozzle plate. A driver IC chip is mounted on the projected portion, and a flexible printed circuit board (also referred to as FPC) is connected to an end portion of the projected portion. Therefore, a region of the actuator unit opposite to the nozzle plate side is occupied by the projected portions of the plurality of cover plates and the FPC connected to the projected portions.
FIG. 7 is a schematic perspective view of a liquid jet head 200 including a two-row head chip 201 having two nozzle rows formed by bonding two actuator substrates 202 and 203 formed of a piezoelectric body. The liquid jet head 200 includes the two-row head chip 201, two circuit boards 204 and 205 for supplying a drive signal to the two-row head chip 201, a relay printed circuit board 212 for supplying a control signal to the two circuit boards 204 and 205, two flexible printed circuit boards 206 and 207 for electrically connecting the two circuit boards 204 and 205 and the two-row head chip 201, and two flexible printed circuit boards 208 and 209 for electrically connecting the relay printed circuit board 212 and the two circuit boards 204 and 205, respectively.
The relay printed circuit board 212 includes a connector 213 for connection to an external device for inputting a control signal from an external circuit, and supplies the input control signal via the two flexible printed circuit boards 208 and 209 to the two circuit boards 204 and 205, respectively. The two circuit boards 204 and 205 include driver ICs 210 and 211, respectively. Each of the driver ICs 210 and 211 generates a drive signal for driving the two-row head chip 201 based on the input control signal. The drive signal generated by the driver IC 210 is supplied via the flexible printed circuit board 206 to the upper actuator substrate 202, while the drive signal generated by the driver IC 211 is supplied via the flexible printed circuit board 207 to the lower actuator substrate 203.
Therefore, the liquid jet head 200 including the two-row head chip 201 requires the two circuit boards 204 and 205, the one relay printed circuit board 212, and the four flexible printed circuit boards 206, 207, 208, and 209.
In the ink jet head described in Japanese Patent Application Laid-open No. 2004-209796, the wiring boards 103 which greatly protrude on a side opposite to the liquid ejection side are located outside the lower substrates 111 forming the respective head chips 101. This increases the weight of the ink jet head, increases the mass of a carriage having a plurality of the ink jet heads mounted thereon, and causes a drive system for driving the carriage to be under a heavy load. Further, regions of the two head chips 101 on the side opposite to the liquid ejection side are occupied by the wiring boards 103, and these regions cannot be effectively used for other devices.
With regard to the ink jet head described in Japanese Patent Application Laid-open No. Hei 10-146974, similarly, the cover plate located between the base plates has the projected portion protruding on the side opposite to the liquid ejection side, and the projected portion is connected to the driver IC chip for driving and to an FPC for transmitting a signal from an external circuit to the driver IC chip. Therefore, the region opposite to the liquid ejection side is occupied by the projected portion and the FPC, and the region cannot be effectively used for other devices.
Further, in the conventionally known liquid jet head illustrated in FIG. 7, in addition to the two-row head chip 201, the four flexible printed circuit boards 206 to 209, the two circuit boards 204 and 205, and the relay one printed circuit board 212 are required. The number of parts is large, and the assembly process of assembling the parts is complicated and takes time. Further, similarly to the cases of Japanese Patent Application Laid-open Nos. 2004-209796 and Hei 10-146974, the two circuit boards, the four flexible printed circuit boards, and the one relay printed circuit board are located in the region opposite to the liquid ejection side. Therefore, there is a limit in forming the region so as to be thin.